Most meat products have to go through the process of pickling in the process to promote the maturity of meat products, increase the flavor of meat products, and stabilize the sensory state of products. In the process of meat processing, due to the different pickling methods and time, and the influence of production technology, packaging and other factors, a variety of products with unique flavor are formed.

From the process point of view, the quality of pickling will affect the next process, and can also determine the final product structure, flavor, color and a series of results. Now with the development of food processing science and technology, people have a new understanding of meat curing, and conducted in-depth research. The curing of meat has been widely used in production as an important processing method, and some basic problems of curing are summarized as follows.

1. meat composition and characteristics

The main components of meat include protein, fat, moisture, ash and other substances. The content of these components will vary due to animal species, age, nutrition, location and other factors. In meat processing, we should not only consider the physical properties and chemical composition of different raw meat, but also consider the difference between water retention and meat color, and the pH value should also be considered. The moisture content of raw meat is generally between 70% and 80%, crude protein is between 17% and 22%, crude fat is generally different according to varieties and parts, and ash content is about 1%.

Meat temperature is a very important part of the processing process, from the slaughter of the flesh began to be contaminated by bacteria, this process is inevitable. For this reason, the temperature control of the meat is a necessary condition for each link, so factors such as room temperature, processing machines, and water temperature are critical to the meat. The amount of time is also a necessary condition for the process. The curing temperature is limited to 3~5 ℃, and the curing time depends on the size and method of the meat. The chopping termination temperature is below 12 ℃, and the temperature suitable for microbial growth should be avoided from 20~40 ℃ for smoking and drying.

Pickling purposes and pickling materials of 2. meat

1, the purpose of pickling    

The purpose of curing has the following aspects: to prevent the spoilage of meat and prolong the storage time; due to the role of nitrate, the meat presents a good color; improve the water retention capacity and binding force of meat; improve the flavor structure of the product by curing and enhance the flavor of meat.

2. Pickling materials and their functions    

(1) Salt    

The main component of salt is Nacl, with a content of more than 85%, in addition to Mg,Ca and other impurities. After salt hydrolysis, sodium ions and chloride ions gather around water molecules to form hydrated ions, and the increase of hydrated ions will lead to the reduction of free water, resulting in the reduction of water activity to a certain extent, when the water activity is less than 0.75, most bacteria and yeast can not grow. When the salt concentration of 1%, its osmotic pressure will destroy the microbial cell membrane, so that it loses water, thereby inhibiting the growth of microorganisms.

In addition, when the enzymes secreted by microorganisms are in a low concentration salt solution, the salt will bind to the peptide in the enzyme protein, and its original shape and structure will be denatured, which will destroy the ability of the enzyme to decompose the meat protein. These environments are not conducive to the growth of microorganisms.

(2) Water holding capacity of meat products    

Refers to the moisture of the meat and the ability to retain moisture added to the meat. The water content of most animal muscles is about 75%. After heating, whether the water can be retained in the original state or the water added from the outside can be well maintained under the action of external conditions. These are all important reasons for determining the quality of the product.

Through experiments, it was found that the ionic strength of sodium chloride was the highest in water retention at 0.8-1.0, and the water retention decreased beyond this standard. Most of the pickling agents are salt, and the water holding capacity is mainly affected by salt during the pickling process. The main substance of meat water holding and binding is the protein in muscle. Under the curing condition, the ionic strength of sodium chloride is about 0.6, and the processing time is 24~48h. Due to the effect of ionic strength, a large amount of myosin in muscle is extracted, which makes the protein in non-dissolved state into dissolved state or from gel state into dissolved state. This shift is the root cause of the increased water holding capacity of the meat.

Myosin in a gel state can also absorb a certain amount of water and swell due to solvation, but this water holding capacity without sufficient ionic strength is very limited. During the heating process, due to protein denaturation, the non-polar group originally included in the protein secondary structure is exposed, and the hydrophobicity of the non-polar group greatly reduces the water holding capacity of the meat. Unsalted meat loses water when heated, which is the reason. After curing, the myosin in the gel state of the meat is transformed into a sol state of considerable concentration, the swelling ability is greatly enhanced, and the process of achieving a high degree of solvation is realized. Under a certain ionic strength, the solvation is the most sufficient and the water holding capacity is the highest. In the process of grinding and chopping, the sol-like myosin is released from the cells and acts as an adhesive. When heated, the sol-like protein forms a huge aggregate, which seals water and fat in the network structure of the aggregate.

Of course, in the actual processing process, a certain amount of pyrophosphate or polyphosphate is often added to increase the extraction of protein, strengthen the binding force between tissues, and improve the water holding capacity of the product.

3. Color mechanism in pickling    

In order to make the cured meat produce bright red, and inhibit the growth of microorganisms and generate a special flavor, nitrate or nitrite is often added to the meat curing preparation. Nitrate is reduced to nitrite by reducing bacteria in the meat, which is generally a product cured for a long time.

We all know that the red substance of meat is mainly myoglobin and hemoglobin in meat, hemoglobin is lost due to animal slaughter. In the presence of nitrite ions, myoglobin reacts with oxygen to generate reddish-brown high-speed myoglobin. Nitrous acid generates nitric oxide by reducing bacteria in meat. Nitric oxide reacts with high-speed myoglobin to generate nitric oxide myoglobin, and generates bright red NO chromogen after heating. In the actual curing process, L-sodium ascorbate, a color aid, is often added to accelerate the reduction of myoglobin, prevent the oxidation of myoglobin, and stabilize the color of meat products.

(1) Residual amount of nitrite    

Nitrous acid is a chemically active substance, which itself acts as an oxidant, releasing O2 into NO; on the contrary, nitrous acid can also be oxidized into nitric acid. Nitrous acid is consumed in the meat at the same time in the reaction, but the consumption of nitrite is not simple, so there is no fixed relationship between nitrite nitrate residue and curing time. In order to ensure the health of consumers, different countries have regulations on nitrite residue.

(2) Other pickling agents    

The main curing agents of salt and nitrite are used in the curing process of meat products. In addition, according to different products, polyphosphate, glucose, Vc, spices, etc. are also added in the curing process to form different flavors. Water retention agent phosphate, mainly sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, pickling due to the addition of phosphate, pH value increases, can improve the water holding capacity of meat, meat tenderness is improved, adhesion is enhanced, we compound with better effect than a single use.

Commonly used 20% sodium hexametaphosphate, 40% sodium tripolyphosphate, 40% sodium pyrophosphate mixed together, generally in accordance with the meat of 0.2~0.5 to add. The addition of spices can increase the special flavor of the product and remove the peculiar smell of the product. Sometimes preservatives and antioxidants are added in the pickling process. This is selected according to the needs of product design, but it has a certain distance from the real purpose of pickling.

(3) Maltol   

There are also in the meat processing without nitrite, but in the processing process with maltol with the use of iron salt, will show the same color as the use of nitrite. The important chemical characteristic of maltol is that it turns purple when it meets iron ions. The iron salt recommended for use can be iron gluconate, iron citrate, etc., which not only achieves color development but also increases the content of trace elements. Maltol accounts for the 0.7 amount of meat, but the formation of microorganisms in the curing process should be controlled. Monascus is a natural pigment extracted from red rice. It is stable in nature and has good staining for protein. The formation of microorganisms should also be considered.

Pickling method of 3. meat

The correct choice of pickling method plays an important role in the post-processing process of the product and the quality and formability of the final product.

(1) Dry-curing method    

The so-called dry curing method is a curing method in which the curing agent is directly mixed with the meat or smeared on the meat surface, or a method in which large meat pieces and meat particles are stirred evenly so as to absorb the curing agent. The advantages of this method are simple operation, less nutrient loss, and high salt concentration and chromogenic agent concentration around the meat block, which inhibits the reproduction of bacteria and is easy to store for a long time. The disadvantage is that fat is easily oxidized. The dry curing method is suitable for Chinese ham, Chinese bacon, dry sausage, air-dried poultry, etc. The dry curing method has a longer cycle and thus has a greater impact on the batch and scale of the product.

(2) Wet pickling method    

Wet pickling method is a pickling method in which a certain concentration of pickling agent solution is prepared in a container in advance, and the pickling agent penetrates into the interior of the meat through diffusion and water transfer to obtain a relatively uniform distribution until its concentration is finally the same as that of the salt solution. Wet pickling method can better promote the maturity of meat, especially the twisted meat, pickled at 0-4 ℃ for 24-48h, the water holding capacity and binding are greatly increased, so as to have a good color, flavor and organizational structure. The disadvantage is that the propagation of microorganisms for a long pickling time will lead to product rancidity, fermentation and other phenomena. Wet pickling is not commonly used now, mainly the introduction of injection and tumbling technology, but some Chinese sauce marinated meat products, non-injection western ham products also use this kind of technology, the products have unique flavor characteristics.

(3) half dry and half wet pickling method    

The pickling method in which the pickling agent is dissolved in a small amount of water and mixed with meat and stirred evenly is called semi-dry and semi-wet pickling method. This method combines the advantages of dry pickling method and wet pickling method and is mostly used in fresh sausage meat and ham.

(4) injection pickling method    

The injection curing method is a more advanced curing method than the previous two methods. It is a new curing method produced with the development of food machinery. It is a pickling method that pre-prepares pickled salt water, uses an injection machine to inject the meat, and then stands or rolls. The injection curing method combines the advantages of wet curing method and dry curing method, which has the advantages of fast dispersion of pickling liquid, short curing period, good effect and high efficiency, and is widely used in meat processing. This method is generally combined with the tumbling process and is an important means of modern meat processing. The injection curing method is suitable for western-style ham, bone-in poultry, Chinese-style soft-packed block meat products, enema products with exposed meat pieces, and some western-style roasted meat.

4. other factors affecting the pickling effect

1 Temperature and time   

High temperature can promote the curing of meat, so that the curing time of meat is shortened on the contrary, the curing time is prolonged, but too high temperature, it will cause the increase of microbial reproduction, easy to make the meat rot. Measures: select the appropriate temperature and time, the general meat curing, the ambient temperature should be 0-4 ℃, the meat temperature should not exceed 7 ℃, in the temperature pickled 18-24h, basically can achieve better pickling quality.

2. Air (oxidation）    

When the meat is cured in the air, the surface of the meat becomes brown due to the action of oxygen. Measures: the upper layer of cured meat should be covered with clean cloth (plastic paper).

3. Compound phosphate  

Excessive use of phosphate affects the color effect of meat, which is due to the high pH value, so the pH value is the best in 6.0. Measures: according to the use of food additives to add standard. General compound phosphate addition ≤ 0.5%. 4) Nitrite or nitrous is the addition of nitrate or nitrous that makes the meat color good, but excessive use, on the one hand, nitrous residue is too high, affecting human health, on the other hand, it is easy to make excess HNO2 in the meat, making the meat produce green substances, if too little use, the color effect will be affected by insufficient nitrous content. Measures: add according to the standard of additive use, I .e. 0.15 g/Kg meat; Use sodium ascorbate and other auxiliary agents in combination with nitrite, but should be added after nitrite.

5. Low-nitrate pickling system    

At present, there is no substitute for nitrite in cured meat products, so a small amount of nitrite needs to be added to the curing system, but other substitutes need to be added. Such substitutes mainly play the role of color aid, bacteriostasis, antitoxin and blocking the formation of nitrosamines. A mixture of 550 mg/kg ascorbate and 550 mg/kg tocopherol was found to be very effective in inhibiting the formation of nitrosamines. The addition amount of nitrite can be reduced to 120 mg/kg, but further toxicity tests and mutation tests are needed.

When lactic acid bacteria are added to meat processing, the amount of sucrose added should be increased, and the amount of nitrite added will be reduced to 40 mg/kg. The sensory and taste are the same as those of nitrite alone. The lactic acid bacteria-producing bacteria can be selected from Streptococcus lactis, Bulgarian bacteria, Lactobacillus acidophilus, and the like. It is better to add lactic acid bacteria at a concentration of 0.2 ~ 1%, and the addition amount of 10 mL/kg can inhibit the reproduction of other bacteria, thus reducing the nitrate content. The tested nitrate addition amount is only 0.01-0.06 of the original.

At present, there are potassium sorbate, lactic acid and salt tannic acid, gallic acid, fumarate, ethylenediaminetetraacetic acid, hypophosphite, etc.

Pickling of meat products is an important means of meat processing. Pickling of meat can improve the flavor and quality of meat products, and improve the preservative and bacteriostatic effect of meat products. However, when pickling meat, we must pay attention to: according to the nature of the product, the correct choice of pickling methods, rational use of pickling agents, pay attention to and strengthen the prevention of influencing factors, only in this way can we ensure the good quality of meat pickling and produce high-quality meat products.